我有以下的code更新帐户表的LINQ to SQL。账户号码是主键列。这需要更新的唯一价值是AccountType;然而，持续时间也将被更新，以零（对于int默认值）。我们怎样才能避免这种不必要的覆盖？

注：我使用的连接方式

注：我理解这种现象的原因。 在DataContext不能一个场之间具有指定值零和一个仅是未分配的区别。。我要寻找一个解决方案来克服这一点。

  [全球:: System.Data.Linq.Mapping.ColumnAttribute（存储=_时间的DbType =诠释NOT NULL
公众诠释时间
 

表中的数据。

表结构：

  CREATE TABLE [DBO]。[帐户]（
[账户号码] [INT] NOT NULL，
[AccountType] [NCHAR]（10）NOT NULL，
[时间] [INT] NOT NULL，
[DepositedAmount] [INT] NULL，
 约束[PK_Account] PRIMARY KEY CLUSTERED
 （
[账户号码] ASC
 ）WITH（PAD_INDEX = OFF，STATISTICS_NORECOMPUTE = OFF，IGNORE_DUP_KEY = OFF，ALLOW_ROW_LOCKS = ON，ALLOW_PAGE_LOCKS = ON）ON [PRIMARY]
 ）ON [PRIMARY]
 

code

 公共无效UpdateAccount（）
    {
        RepositoryLayer.Account ACC1 =新RepositoryLayer.Account（）;
        acc1.AccountNumber = 4;
        acc1.AccountType =验证;

        accountRepository.UpdateChangesByAttachAndRefresh（ACC1）;
        accountRepository.SubmitChanges（）;

    }


    公共虚拟无效UpdateChangesByAttachAndRefresh（T实体）
    {

        //可以GetOriginalEntityState造成任何错误？它是不必要的？
        如果（GetTable（）。GetOriginalEntityState（实体）== NULL）
        {
            //如果它尚未附

            Context.GetTable＆LT; T＆GT;（）附加（实体）。
            Context.Refresh（System.Data.Linq.RefreshMode.KeepCurrentValues​​，实体）;


        }

    }
 

生成的SQL

 更新[DBO]。[帐户]
SET [AccountType] = @ P3，[时间] = @ P4
WHERE（[账户号码] = @ P0）
与（[AccountType] = @ p​​1）为
AND（[时间] = @ P2）
与（DepositedAmount] IS NULL）

 -  @ P0：输入INT（尺寸= -1; preC = 0;规模= 0）[4]
 -  @ P1：输入NCHAR（大小= 10; preC = 0;规模= 0）[测试]
 -  @ P2：输入INT（尺寸= -1; preC = 0;规模= 0）[10]
 -  @ P3：输入NCHAR（大小= 10; preC = 0;规模= 0）[确认]
 -  @ P4：输入int（尺寸= -1; $ P $件= 0;量表= 0）[0]

 - 背景：sqlProvider的（SQL2008）型号：AttributedMetaModel体形：4.0.30319.1
 

阅读：

Can LINQ到SQL省略上插入未指定的列，以便数据库使用默认值？

How我可以绑定一个枚举到位的的DbType或INT？

Linq到SQL：为什么我会得到IDENTITY_INSERT错误

LINQ到SQL：更新无刷新的时候UpdateCheck的=从不

我通过修改更新的方式解决了这个问题，通过执行LINQ到SQL：更新无刷新的时候UpdateCheck的=从不

UpdateCheck的设置为从不为持续时间列

 公共无效UpdateAccount（）
    {
        //从previous使用的值选择
        日期时间previousDateTime =新的日期时间（2012年，6，26，11，14，15，327）;
        INT prevDuration = 0;

        RepositoryLayer.Account accEntity =新RepositoryLayer.Account（）;
        accEntity.AccountNumber = 1; //首要的关键
        accEntity.ModifiedTime = previousDateTime; //并发列
        //accEntity.Duration = prevDuration;

        accountRepository.UpdateChangesByAttach（accEntity）;

        //值后附加修改
        accEntity.AccountType =双赢
        accEntity.ModifiedTime = DateTime.Now;

        尝试
        {
            accountRepository.SubmitChanges（）;
        }
        赶上（System.Data.Linq.ChangeConflictException E）
        {
            抛出新的异常（e.Message）;
        }

    }


   公共虚拟无效UpdateChangesByAttach（T实体）
    {

        如果（Context.GetTable＆LT; T＆GT;（）GetOriginalEntityState（实体）== NULL）
        {
            //如果它尚未附
            Context.GetTable＆LT; T＆GT;（）附加（实体）。
        }

    }
 

生成的SQL

 更新[DBO]。[帐户]
SET [AccountType] = @ P2，[ModifiedTime] = @ P3
WHERE（[账户号码] = @ P0）
      与（[ModifiedTime] = @ p​​1）为

 -  @ P0：输入INT（尺寸= -1; preC = 0;规模= 0）[1]
 -  @ P1：输入的日期时间（尺寸= -1; preC = 0;规模= 0）[2012年6月26日上午11时十四分15秒]
 -  @ P2：输入NCHAR（大小= 10; preC = 0;规模= 0）[WIN-WIN]
 -  @ P3：输入的日期时间（尺寸= -1; preC = 0;规模= 0）[2012年6月26日上午11点16分29秒]
 

I have the following code for updating Account table with LINQ to SQL. AccountNumber is the primary key column. The only value which need to be updated is AccountType; however the Duration also gets updated with zero (default value for int). How can we avoid this unnecessary overwrite?

Note: I am using Attach method

Note: I understand the reason for this behavior. "The DataContext cannot distinguish between a field with an assigned value of zero and one that is merely unassigned.". I am looking for a solution to overcome this.

[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_Duration", DbType="Int NOT NULL"
public int Duration

Table DATA

Table Structure:

 CREATE TABLE [dbo].[Account](
[AccountNumber] [int] NOT NULL,
[AccountType] [nchar](10) NOT NULL,
[Duration] [int] NOT NULL,
[DepositedAmount] [int] NULL,
 CONSTRAINT [PK_Account] PRIMARY KEY CLUSTERED 
 (
[AccountNumber] ASC
 )WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
 ) ON [PRIMARY]

CODE

    public void UpdateAccount()
    {
        RepositoryLayer.Account acc1 = new RepositoryLayer.Account();
        acc1.AccountNumber = 4;
        acc1.AccountType = "Verify";

        accountRepository.UpdateChangesByAttachAndRefresh(acc1);
        accountRepository.SubmitChanges();

    }


    public virtual void UpdateChangesByAttachAndRefresh(T entity)
    {

        //Can GetOriginalEntityState cause any bug? Is it unnecessary?           
        if (GetTable().GetOriginalEntityState(entity) == null)
        {
            //If it is not already attached

            Context.GetTable<T>().Attach(entity);
            Context.Refresh(System.Data.Linq.RefreshMode.KeepCurrentValues, entity);


        }

    }

Generated SQL

UPDATE [dbo].[Account]
SET [AccountType] = @p3, [Duration] = @p4
WHERE ([AccountNumber] = @p0) 
AND ([AccountType] = @p1) 
AND ([Duration] = @p2) 
AND ([DepositedAmount] IS NULL)

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [4]
-- @p1: Input NChar (Size = 10; Prec = 0; Scale = 0) [TEST      ]
-- @p2: Input Int (Size = -1; Prec = 0; Scale = 0) [10]
-- @p3: Input NChar (Size = 10; Prec = 0; Scale = 0) [Verify]
-- @p4: Input Int (Size = -1; Prec = 0; Scale = 0) [0]

-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1

READING:

Can LINQ-to-SQL omit unspecified columns on insert so a database default value is used?

How can I bind an Enum to a DbType of bit or int?

Linq to SQL: Why am I getting IDENTITY_INSERT errors?

LINQ to SQL: Updating without Refresh when "UpdateCheck = Never"

I solved this issue by changing the update approach by following the answer in LINQ to SQL: Updating without Refresh when "UpdateCheck = Never"

UpdateCheck is set as Never for the Duration column

    public void UpdateAccount()
    {
        //Used value from previous select
        DateTime previousDateTime = new DateTime(2012, 6, 26, 11, 14, 15, 327);
        int prevDuration = 0;

        RepositoryLayer.Account accEntity = new RepositoryLayer.Account();
        accEntity.AccountNumber = 1; //Primary Key
        accEntity.ModifiedTime = previousDateTime; //Concurrency column
        //accEntity.Duration = prevDuration;

        accountRepository.UpdateChangesByAttach(accEntity);

        //Values to be modified after Attach
        accEntity.AccountType = "WIN-WIN";
        accEntity.ModifiedTime = DateTime.Now;

        try
        {
            accountRepository.SubmitChanges();
        }
        catch(System.Data.Linq.ChangeConflictException e)
        {
            throw new Exception(e.Message);
        }

    }


   public virtual void UpdateChangesByAttach(T entity)
    {

        if (Context.GetTable<T>().GetOriginalEntityState(entity) == null)
        {
            //If it is not already attached
            Context.GetTable<T>().Attach(entity);
        }

    }

Generated SQL

UPDATE [dbo].[Account]
SET [AccountType] = @p2, [ModifiedTime] = @p3
WHERE ([AccountNumber] = @p0) 
      AND ([ModifiedTime] = @p1)

-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1]
-- @p1: Input DateTime (Size = -1; Prec = 0; Scale = 0) [6/26/2012 11:14:15 AM]
-- @p2: Input NChar (Size = 10; Prec = 0; Scale = 0) [WIN-WIN]
-- @p3: Input DateTime (Size = -1; Prec = 0; Scale = 0) [6/26/2012 11:16:29 AM]